<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>圆角边框</title>
    <style>
        div {
            width: 100px;
            height: 100px;
            border: 1px solid black;
        }

        div:nth-of-type(1) {
            border: 5px solid black;
            border-radius: 20px;
        }

        div:nth-of-type(2) {
            margin: 8px auto;
            height: 50px;
            border-radius: 50px 50px 0 0;
            box-shadow: 10px 10px 5px orangered;
        }

    </style>
</head>
<body>

<div></div>
<div></div>

</body>
</html>